1. Field of the Disclosure
The present invention relates to a low-density polyethylene nanocomposite comprising 5% by weight or more of nanoscale fillers of montmorillonite clay, silica and zinc oxide, a method for making the low-density polyethylene nanocomposite, and determination of changed weatherability and durability of the nanocomposite due to the nanoscale fillers.
2. Description of Related Art
Industrial and research interest in thermoplastic nanocomposites stems from the expectation that nanoscale fillers potentially impart dramatically improved properties at low loading. This is reasonable because of the high particle densities (106-108 particles per sq. micron), the exceptionally high interfacial area generated (103-104 sq. m. per ml) and proximity of particles in the matrix (Vaia R. A. and Wagner H. D. (2004) Framework for nanocomposites Mater Today, 7:32-7—incorporated by reference in its entirety). Increased interphase volume at the same volume fraction of filler is particularly advantageous as it is this volume that yields the superior properties of any composite (Schadler L. S. (2003) Polymer-based and polymer-filled nanocomposites In: Ajayan P M, Schadler L S, Braun P V, editors. Nanocomposite science and technology, Weinheim, Germany: Wiley-VCH—incorporated by reference in its entirety).
The specific surface area is particularly large in layered silicate clays including Montmorillonite clay (MMT) which is a superior nanofiller especially when the polymer is intercalated between the plate-like morphology. This is achieved in the laboratory with in-situ polymerization or template synthesis in the matrix (Utracki L. A., Sepehr M., Boccaleri E. (2007) Polymer Advanced Technologies, 18:1-37; Utracki L. A., Sepehr M., Boccaleri E. (2007) Polymer Advanced Technologies, 18:1-37; Cheng W., Miao W., Peng J., Zou W., Zhang L. (2009) Iranian Polymer Journal, 18, pp. 365-371; Zhang J. G. and Wilkie C. A. (2003) Polymer Degradation and Stability, 80, pp. 163-169; Zhang M. Q., Rong M. Z., Zhang H. B., Friedrich K. (2003) Polymer Engineering & Science, 43, pp. 490-500; Gopakumar T. G., Lee J. A., Kontopoulou M., Parent J. S. (2002) Polymer, 43, pp. 5483-5491—incorporated by reference in its entirety). However, industrial applications are likely to rely on melt-intercalation, often with the use of a compatibilizer (Wang K. H., Choi M. H., Koo C. M., Xu M. Z., Chung I. J., Jang M. C. (2002) Journal of Polymer Science, Part B: Polymer Physics, 40, pp. 1454-1463; Wang K. H., Chung I. J., Jang M. C., Keum J. K., Song H. H. (2002) Macromolecules, 35, pp. 5529-5535; Sanchez-Valdes S., Lopez-Quintanilla M. L., Ramirez-Vargas E., et al., (2006), Macromolecular Materials and Engineering, 291, pp. 128, 2006—incorporated by reference in its entirety). The blending is carried out usually in a compounding extruder. Melt compounding is more likely to break-up aggregates and facilitate good dispersion with simple nanoparticles. This is particularly true of layered silicate nanofillers such as MMT. Nanoparticles, having no layered structure have relatively lower specific surface area, but are relatively easier to disperse in the polymer matrix.
Successful incorporation of nanomaterials into thermoplastics and melt blending of clay and silica with polyethylene can be successfully achieved (Wei L., Tang T., Huang B. (2004) Journal of Polymer Science Part A: Polymer Chemistry, 42, pp. 941-949; Zhang J. G. and Wilkie C. A. (2003) Polymer Degradation and Stability, 80, pp. 163-169; Zhang M. Q., Rong M. Z., Zhang H. B., Friedrich K. (2003) Polymer Engineering & Science, 43, pp. 490-500—incorporated by reference in its entirety). For instance, Sanchez et al. studied polyethylene/MMT nanocomposites films prepared by melt blending low-density polyethylene (LDPE) with MMT using maleic anhydride grafted polyethylene (LDPE-g-MA) as a compatibilizer (Sanchez-Valdes S., Lopez-Quintanilla M. L., Ramirez-Vargas E., et al., (2006), Macromolecular Materials and Engineering, 291, pp. 128, 2006—incorporated by reference in its entirety).